Organosilanes, particularly methylsilane (CH3SiH3) and trimethylsilane ((CH3)3SiH), are raw material gases that are useful as CVD film-forming materials in semiconductor device production. Particularly in recent years, they attract attention as raw material gases of low-dielectric-constant insulating films. In methods for producing organosilanes, it is general to use a method in which a reducing agent, such as aluminum lithium hydride (LiAlH4), is used in a polar organic solvent, such as diethyl ether (C2H5OC2H5), dimethoxyethane (DME), diglyme (DGM) or tetrahydrofuran (THF). It is superior in product purity and yield, too. Hitherto, it has been considered that the reduction reaction by LiAlH4 occurs only in a polar solvent and that the reaction does not occur in a non-polar hydrocarbon series solvent such as hexane and heptane. There have been no publications or the like having disclosures other than reaction examples using polar solvents as reaction solvents of organosilanes. Although a LiAlH4 reduction of cyclohexanone has been tried in toluene solvent that is one of aromatic hydrocarbon series organic solvents used in the present invention, cyclohexanol that should be obtained by the reduction has not been found (Non-patent Publication 1). It is generally considered that AlH4− ion is produced in an organic solvent by dissociation in LiAlH4 reduction, and this acts on the reaction substance to generate the reaction. Therefore, it is considered that the reaction proceeds only in a polar solvent that can dissolve LiAlH4 and that the reaction does not occur since it is not possible to dissolve LiAlH4 in a solvent that has little polarity, such as toluene.
As an organosilane synthesis example using a polar solvent, there is described a method for synthesizing (CH3)3SiH with a yield of 85% by reacting trimethylchlorosilane ((CH3)3SiCl) with LiAlH4 under reflux at a temperature of 86° C. using DME solvent (Non-patent Publication 2). Furthermore, there is described a method for synthesizing (CH3)3SiH with a yield of 91% by reacting ethoxytrimethylsilane ((CH3)3SiOC2H5) with LiAlH4 at a temperature of 50-70° C. using DGM solvent (Patent Publication 1).
However, in these methods using polar solvents, organosilanes that are in salvation remain in the residual liquids after the termination of the reactions. The difficulty in their recovery caused lowering of yield. In the case of treating the reaction residual liquid, it was difficult to recover the solvent by the treatment with water, since all of the solvents other than diethyl ether are water-soluble. Even in the case of using a method of recovering the solvent from the reaction residual liquid through evaporation, a separation from the residue was difficult due to high polarity of the solvent, and the solvent recovery use was extremely difficult.
Patent Publication: WO 01/58908
Non-patent Publication 1: J. Chem. Res. (S), 1, 24 (1990)
Non-patent Publication 2: J. Amer. Chem. Soc., 83, 1916 (1961)